1. Field of the Invention
The present invention relates to a drive shaft structure, a turbo compressor, and a turbo refrigerator.
Priority is claimed on Japanese Patent Application No. 2010-087858, filed Apr. 6, 2010, the content of which is incorporated herein by reference.
2. Background Art
As a refrigerator cooling or freezing a cooling object such as water, there has been known a turbo refrigerator including a turbo compressor compressing and discharging a refrigerant gas. This kind of turbo compressor may include a flow rate control unit that adjusts the flow rate of a refrigerant gas flowing inside the turbo compressor in order to adjust the cooling capability of the turbo refrigerator (for example, refer to Japanese Patent Application, First Publication No. 2007-177695). The flow rate control unit is provided inside the casing of the turbo compressor, and the flow rate control unit may adjust the passage width of the refrigerant gas is adjusted or use a plurality of blade members rotatably provided inside the passage of the refrigerant gas. A drive unit, such as a motor for driving the flow rate control unit, is provided at the outside of the casing. The drive unit is connected to the flow rate control unit through a drive shaft. The drive shaft is a shaft member that transmits the drive force generated by the drive unit to the flow rate control unit. Since the drive shaft is provided so as to penetrate the casing, a seal member (packing or the like) is provided while coming into close contact with the outer peripheral surface of the drive shaft so as to prevent the refrigerant gas from leaking from the periphery of the drive shaft.
In the turbo refrigerator, since the flow rate control unit is provided inside the casing of the turbo compressor, it is difficult to confirm the operation thereof from the outside of the casing. For this reason, an index mark may be formed at a visible position of the outer peripheral surface of the drive shaft so as to confirm and inspect the operation of the flow rate control unit. The index mark may be formed by, for example, a punch.
However, when the index mark is formed by the punch, burrs are formed around the index mark. Further, it is necessary to disassemble and assemble again the drive shaft and the seal member to confirm the interior of the turbo compressor during, for example, maintenance.
That is, since the seal member is provided while coming into close contact with the outer peripheral surface of the drive shaft, there is a possibility that the seal member is damaged due to burrs upon disassembling or assembling the drive shaft and the seal member when burrs are formed at the outer peripheral surface due to the index mark. Since the air-tightness around the drive shaft may not be ensured when the seal member is damaged, the damaged seal member needs to be replaced with new one. Therefore, there is a problem in that maintenance cost of the turbo compressor increases.
The invention is made in view of such circumstances, and an object thereof is to provide a drive shaft structure capable of preventing the seal member from being damaged upon disassembling and assembling the drive shaft and the seal member, a turbo compressor, and a turbo refrigerator.